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Exotic mesons, particles that have quantum numbers that are inaccessible to conventional quark-model mesons, are predicted by quantum chromodynamics (QCD), but past experiments seeking to identify exotic candidates have produced controversial results. The HyCLAS experiment (E04005) at Thomas Jefferson National Accelerator Facility (TJNAF) proposes the use of the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) in Hall B to study the photoproduction of exotic mesons. However, the base detector package at CLAS is not ideal for observing and measuring neutral particles, particularly at forward angles. The Deeply Virtual Compton Scattering (DVCS) experiment at TJNAF has commissioned a new calorimeter for detecting small-angle photons, but studies must be performed to determine its suitability for a meson spectroscopy experiment. The [eta][pi] system has been under especial scrutiny in the community as a source for potential exotics, so the new calorimeter's ability at reconstructing these resonances must be evaluated. To achieve this, the invariant mass of showers in the calorimeter are reconstructed. Also, two electroproduction reaction channels analogous to photoproduction channels of interest to HyCLAS are examined in DVCS data. It is found that, while not ideal, the new calorimeter will allow access to additional reaction channels, and its inclusion in HyCLAS is warranted. Results in basic shower reconstruction show that the calorimeter has good effi ciency in resolving [pi]° decays, but its [eta] reconstruction is not as strong. When examining ep → ep[pi]°[eta], preliminary reconstruction of the [eta][pi]° system shows faint signals in the a0(980) region. In the ep → e n [pi]+ [eta] channel, preliminary reconstruction of the [eta][pi]+ system gave good signals in the a0(980) and a2(1320) regions, but statistics were poor. While more analyses are necessary to improve statistics and remove background, these preliminary results support the claim that the DVCS calorimeter will be a valuable addition to CLAS for upcoming exotic meson searches in photoproduction.Read more...

Published through SciTech Connect.01/01/2007.Journal of Undergraduate Research 7 FT.

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1 online resource (10-14 : digital, PDF file.)

Abstract:

Exotic mesons, particles that have quantum numbers that are inaccessible to conventional quark-model mesons, are predicted by quantum chromodynamics (QCD), but past experiments seeking to identify exotic candidates have produced controversial results. The HyCLAS experiment (E04005) at Thomas Jefferson National Accelerator Facility (TJNAF) proposes the use of the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) in Hall B to study the photoproduction of exotic mesons. However, the base detector package at CLAS is not ideal for observing and measuring neutral particles, particularly at forward angles. The Deeply Virtual Compton Scattering (DVCS) experiment at TJNAF has commissioned a new calorimeter for detecting small-angle photons, but studies must be performed to determine its suitability for a meson spectroscopy experiment. The [eta][pi] system has been under especial scrutiny in the community as a source for potential exotics, so the new calorimeter's ability at reconstructing these resonances must be evaluated. To achieve this, the invariant mass of showers in the calorimeter are reconstructed. Also, two electroproduction reaction channels analogous to photoproduction channels of interest to HyCLAS are examined in DVCS data. It is found that, while not ideal, the new calorimeter will allow access to additional reaction channels, and its inclusion in HyCLAS is warranted. Results in basic shower reconstruction show that the calorimeter has good effi ciency in resolving [pi]° decays, but its [eta] reconstruction is not as strong. When examining ep → ep[pi]°[eta], preliminary reconstruction of the [eta][pi]° system shows faint signals in the a0(980) region. In the ep → e n [pi]+ [eta] channel, preliminary reconstruction of the [eta][pi]+ system gave good signals in the a0(980) and a2(1320) regions, but statistics were poor. While more analyses are necessary to improve statistics and remove background, these preliminary results support the claim that the DVCS calorimeter will be a valuable addition to CLAS for upcoming exotic meson searches in photoproduction.